Used as an amine-reactive crosslinking reagent in bioconjugation, particularly in the preparation of antibody-drug conjugates (ADCs) and protein labeling. The azide group enables click chemistry reactions, such as copper-catalyzed azide-alkyne cycloaddition (CuAAC), allowing efficient and selective attachment of payloads like fluorophores, drugs, or biotin to biomolecules. The active ester reacts with primary amines on proteins or peptides under mild conditions, forming stable amide bonds. Its bifunctional design makes it valuable in pharmaceutical research, diagnostics, and targeted therapy development.